Manual

10
2. Remove horizontal (metal) duct covers to access vertical
(downflow) discharge duct knockouts in unit base.
3. Use a screwdriver and hammer to remove the panels in the
bottom of the unit base (See Fig. 10).
4. If unit ductwork is to be attached to vertical opening flanges
on the unit base (jackstand applications only), do so at this
time.
PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in property
damage.
Collect ALL screws that were removed. Do no t leave
screws on rooftop as permanent damage to the roof may
occur .
CAUTION
!
5. It is recommended that the base insulation around the
perimeter of the vertical return--air opening be secured to
the base with aluminum tape. Applicable local codes may
require aluminum tape to prevent exposed fiberglass.
6. Cover both horizontal duct openings with the provided duct
covers. Ensure opening is air-- and watertight.
7. After completing unit conversion, perform all safety checks
and power up unit.
NOTE: The design and installation of the duct system must be in
accordance with the standards of the NFPA for installation of
nonresidence-- type air conditioning and ventilating systems, NFPA
90A or residence--type, NFPA 90B; and/or local codes and
ordinances.
SUPPLY
DUCT
OPENING
RETURN
DUCT
OPENING
VENT HOOD
SHIPPING
LOCATION
A05143
Fig. 9 -- Supply and Return Duct Opening
DUCT COVERS REMOVED
C99012
Fig. 10 -- Vertical Duct Cover Removed
Adhere to the following criteria when selecting, sizing, and
installing the duct system:
1. Units are shipped for horizontal duct installation (by
removing duct covers).
2. Select and size ductwork, supply-- air registers, and
return--air grilles according to American Society of Heating,
Refrigeration and Air Conditioning Engineers (ASHRAE)
recommendations.
3. Use flexible transition between rigid ductwork and unit to
prevent transmission of vibration. The transition may be
screwed or bolted to duct flanges. Use suitable gaskets to
ensure weather--tight and airtight seal.
4. All units must have field--supplied filters or accessory filter
rack installed in the return--air side of the unit.
Recommended sizes for filters are shown in T able 1.
5. Size all ductwork for maximum required airflow (either
heating or cooling) for unit being installed. Avoid abrupt
duct size increases or decreases or performance may be
affected.
6. Adequately insulate and weatherproof all ductwork located
outdoors. Insulate ducts passing through unconditioned
space, and use vapor barrier in accordance with latest issue
of Sheet Metal and Air Conditioning Contractors National
Association (SMACNA) and Air Conditioning Contractors
of America (ACCA) minimum installation standards for
heating and air conditioning systems. Secure all ducts to
building structure.
7. Flash, weatherproof, and vibration isolate all openings in
building structure in accordance with local codes and good
building practices.
Table 2 – Maximum Gas Flow Capacity*
NOMINAL
IRON PIPE
SIZE (IN.)
INTERNAL
DIAMETER
(IN.)
LENGTH OF PIPE (FT)†
10 20 30 40 50 60 70 80 90 100 125 150 175 200
1/2 .622 175 120 97 82 73 66 61 57 53 50 44 40 — —
3/4 .824 360 250 200 170 151 138 125 118 110 103 93 84 77 72
1 1.049 680 465 375 320 285 260 240 220 205 195 175 160 145 135
1--1/4 1.380 1400 950 770 600 580 530 490 460 430 400 360 325 300 280
1--1/2 1.610 2100 1460 1180 990 900 810 750 690 650 620 550 500 460 430
*Capacity of pipe in cu ft of gas per hr for gas pressure of 0.5 psig or less. Pressure drop of 0.5 ---in. wc (based on a 0.60 specific gravity gas). Refer to Table,
National Fire Protection Association NFPA 54.
{ This length includes an ordinary number of fittings.
574D